1. Technical Field
This invention relates generally to the manufacture of powder metal articles, and more particularly to articles having a densified outer surface.
2. Related Art
It is known in the art to surface densify compacted and sintered powder metal articles in order to develop a densified layer of the powdered metal material on a surface of the article. Prior U.S. Pat. Nos. 6,017,489 and 6,168,754, which are commonly owned by the assignee of the present invention, disclose multi-stage densifying tools having a series of linearly spaced, progressively sized forming portions which, when forced across an outer or inner surface of the powder metal preform develop a densified layer of the material at the surface.
A particular challenge comes when the surface to be densified is a blind surface that is inaccessible from both ends, such as the outer surface of a hub extending from a radially larger base of a component or the inside wall of a closed or blocked end sleeve. Prior U.S. Pat. No. 5,540,883 teaches a process of densifying such blind surfaces by means of a roll forming operation in which a forming tool is forcibly rolled against the blind surface in the direction of its perimeter to yield a densified layer. However, depending upon the shape and accessibility of the particular surface, densification by roll forming may not be practically or economically feasible.
It is an object of the present invention to advance the art by providing a process which overcomes or greatly minimizes the foregoing limitations of the prior art processes.